6.1. SoE assessment from available information
Nationally-defined objectives under the NZCPS are generally relatively broad, and do not prescribe state of the environment monitoring requirements. Protection of
indigenous biodiversity, maintenance or improvement of water quality for ecosystem functioning or human uses, and monitoring of sedimentation levels and impacts are requirements relevant to the state of the coastal environment. Fishing activity is not considered in the NZCPS, and is substantially outside of the control of councils.
Nonetheless, it is an important component of environmental health as the changes caused in soft sediment habitats are substantial, as are effects on targeted species and the wider food web.
No process to define regional values or management aims has occurred for the area of the CMA considered here (i.e., the sub-tidal outer coast). Key aspects of
ecosystem health can nonetheless be identified on the basis of local and national knowledge.
Fundamental dynamics of the water column environment have been described in research projects and reports. The seabed environment has been described
qualitatively from historical material, research, and monitoring projects. Quantitative sampling of the seabed has occurred for a range of research and monitoring projects, and this could be compiled to map the current community structure across the bay.
Direct effects of those anthropogenic stressors which occur immediately in the marine environment are quite well understood. Fisheries data, consent-associated
monitoring, research projects, and marine reserve monitoring all contribute to this knowledge.
In terms of key topics considered for gauging ecosystem health status (discussed in Section 5), we can state the following:
Primary productivity: nutrient input to the bays is ocean-dominated, and the region seems at limited risk overall of eutrophication. However, nearshore and local- scale effects of nutrient inputs may occur. Phytoplankton removal can occur in association with mussel farming, but no large-scale reduction is apparent.
Sedimentation: In the last two decades land-based sediment inputs have not been exceptionally high. However, previously deposited sediments are strongly impacted by disturbance (see Habitat integrity below), and high levels of
suspended sediment have been detected in the water column. Re-suspension of previously deposited sediment is apparently a greater stressor than new sediment input to Tasman Bay and Golden Bay. Benthic sediment texture may be a more important indicator than sediment deposition, as fine sediments are more easily re-suspended.
Habitat integrity: Disturbance by fishing has substantially modified soft-sediment habitats, homogenising sediments and reducing biogenic structure within the bays. Many documented communities are characteristic of disturbed
environments, but the extent and status of remaining biogenic habitat is not well understood. Less is known about rocky reef habitats, where monitoring focusses on mobile fauna.
Contamination: Overall, bacterial contamination appears to be low in coastal waters of the bays, but occasional peaks occur, often following periods of rainfall.
Non-consented land-based activity can be a greater cause of bacterial
contamination than consented activity. Chemical contamination from consented activity is low-level, and levels high enough to potentially have ecological impacts do not occur on the outer coast.
Fisheries: Important fish stocks are depleted compared to historical levels within the bays, which suggests that substantial changes to the food-web have also occurred. Protected areas show an increase in the numbers of some exploited species. There is some evidence to suggest that fishing is having food-web effects on rocky reefs.
Invasive species: Biosecurity surveys at ports within the bays have found a
number of established invasive species, but substantial negative impacts have not been documented.
6.2. Gaps analysis for assessment of the state of the marine environment
Understanding of environmental processes is important to provide context for
observed changes, however many national and international gaps exist. For example, there is generally poor understanding of the impact of land-based stressors in the marine environment (Morrison et al. 2009). On a local level, most of the ecological studies that have been carried out on the bays’ water column and seabed have been observational and the nature and magnitude of biogeochemical processes have been inferred, obtained from the international literature, or in some cases deduced by numerical modelling. There have been few experimental studies that have attempted to obtain realistic in situ rates of nutrient assimilation, remineralisation (e.g.
ammonification), recycling (e.g. nitrification) and loss (e.g. de-nitrification), or attempted to identify and quantify the environmental factors that control them.
Relatively limited environmental knowledge is a fundamental challenge of working in the marine environment. Many knowledge gaps are beyond the scope or ability of a council-driven project to solve, but these gaps should be acknowledged and the related uncertainty included in planning decisions. Moreover, contributions to national reporting, and integration of monitoring activity and data sources can contribute to improving the understanding of the marine environment on a regional and national scale.
Most of the information available on the outer coastal environment of Tasman Bay and Golden Bay was not collected for the purpose of measuring the state of the environment. The ability to assess state and trends is therefore limited. Considering the information available at a regional level, the most fundamental issue in
determining the state of the environment in Tasman Bay and Golden Bay is the lack of comparable long-term data. Another limitation is lack of spatial replication,
particularly in terms of water column monitoring. While TASCAM is a useful resource, it was located to capture impacts from the Motueka River plume. It would be
extremely valuable to have other buoys deployed in other parts of the bay to provide comparative data. Collection of data from other areas in the bay would also provide for calibration of algorithms to apply to satellite imagery. This could then provide historical (~12 year) data on surface water parameters throughout the bay.
Many of the topics outlined above (Section 6.1) are interrelated, and assessment of the state of the environment requires consideration of interactions between different components of the ecosystem. For example, suspended sediments can impact seabed and water column primary productivity, prevent recovery of biogenic habitat integrity, and mediate contaminant persistence and dispersal. Sediment resuspension is a prime example of a cumulative effect. The impacts of terrestrial sediment input are exacerbated by disturbance, both from direct fishing disturbance, and because the removal of shellfish has left seafloor sediments more exposed to water
movement. Less filtering of particles from the water occurs in the absence of abundant shellfish, which may limit recovery of shellfish populations. Moreover, climate change is expected to exacerbate the situation as increased frequency and severity of storm events will lead to increased wave action and higher sediment input from land.
Many aspects of ecosystem functioning are expected to change with the progress of climate change. For example, changes in temperature will influence the stratification dynamics of the water column, which affects primary productivity. Ocean acidification is also expected to impact the production of calcified structures such as bivalve shells, thereby adding further to the impacts on biogenic habitat formation, as well as other impacts on commercially and ecologically important species. Monitoring is prescribed on a consent-by-consent basis, and no system exists for integrating information across consents. Accordingly, there is no means for identification and assessment of cumulative effects, and insufficient background information exists to provide context for the impacts of climate change.
Requirements beyond current information and data collection are therefore:
Greater temporal resolution: Plan for more extensive on-going monitoring, where appropriate building on existing data (e.g., marine reserve monitoring, past research projects).
Better representation of spatial variability: Identify sites which represent a range of degrees of impact (e.g., within / away from river plumes, fishing activity, etc) and
habitat types (stations suited to assessment of water column, soft sediment, reef habitat, significant sites)
Targeting of data to assess the of state of the marine environment
o identification of relevant indicators and standards to inform ecosystem health status assessments
o data collection and management designed to identify
impacts of land-based stressors
impacts of fishing activity
assessment of degree and impacts of climate change 37
cumulative impacts38
o stability of data collection over time (less dependence on consenting requirements and research projects for data collection)
o better data sharing across users (the material in Newcombe &
Cornelisen (2014) and Forrest & Cornelisen (2015) and associated reports provide framework approaches for information integration)
Alignment (or a view to future alignment) with other councils, and national strategies such as MfE reporting requirements.
Ideally a process would be undertaken to define values and management objectives for the marine environment. The Marine Futures process currently underway in Marlborough39 may provide a useful model for such an approach in Tasman Bay and Golden Bay. Engagement with iwi regarding aspirations for coastal health is also lacking. It would be appropriate to establish relationships and processes that provide for kaitiaki aspirations for the coastal environment and for cultural monitoring activity.
37 A recent proposal on ocean acidification was submitted in the 2015 MBIE contestable round; if successful, the project will include expansion of TASCAM to include monitoring of pH and dissolved oxygen.
38 Atlantis (atlantis.cmar.csiro.au) is an ecosystem model that can be used as a predictive management tool that may assist in filling some of these gaps. Atlantis was developed by CSIRO in Australia, and is being applied to the Tasman Bay and Golden Bay environment in a NIWA project. In the current version, the bay is divided into 25 areas that are defined by factors such as substrate type, water temperature, and fishing intensity. Small areas, such as patch reef or even the Hororoirangi Marine Reserve are too small to be explicitly considered, although future versions may be able to consider more fine-scale habitat definition. The model is still under development, and more data types, such as details of fishing activity and gear, could be added to improve model relevance and predictive ability. In theory the Atlantis model could be used to assess the impacts of management changes such as protection from fishing activity over different areas of the bays, or to predict climate change impacts.
39 www.marlmarinefutures.co.nz